Posted
by
ScuttleMonkey
on Monday December 05, 2005 @04:24PM
from the flushing-out-the-noise dept.

D2Deek writes "Science Daily is reporting on a new device called an Optical Vortex Coronagraph that's been invented to directly image planets orbiting other stars by using a special lens that "spins out" the light from the star leaving only the reflected light from the planet." I just can't imagine trying to clean a lens shaped like a giant corkscrew.

This is actually more about the angle of light, say I want to capture all light in a very tight.005% angle. Unfortunatly there is a sun at the very very edge of my shot. Even though its technically out of the angle of my shot with conventional lenses the sun will glare through. This technology allows light at the edges of the lense to be spun off. It really has nothing to do with intensity.

A new optical device might allow astronomers to view extrasolar planets directly without the annoying glare of the parent star. It would do this by "nulling" out the light of the parent star by exploiting its wave nature, leaving the reflected light from the nearby planet to be observed in space-based detectors.

About ten years ago, the presence of planets around stars other than our sun was first deduced by the very tiny wobble in the star's spectrum of light imposed by the mutual tug between the star and its satellite. Since then, more than 100 extrasolar planets have been detected in this way. Also, in a few cases the slight diminution in the star's radiation caused by the transit of the planet across in front of the star has been observed. Many astronomers would, however, like to view the planet directly, a difficult thing to do.

Seeing the planet next to its bright star has been compared to trying to discern, from a hundred meters away, the light of a match held up next to the glare of an automobile's headlight. The approach taken by Grover Swartzlander and his colleagues at the University of Arizona is to eliminate the star's light by sending it through a special helical-shaped mask, a sort of lens whose geometry resembles that of a spiral staircase turned on its side.

The process works in the following way: light passing through the thicker and central part of the mask is slowed down. Because of the graduated shape of the glass, an "optical vortex" is created: the light coming along the axis of the mask is, in effect, spun out of the image. It is nulled, as if an opaque mask had been placed across the image of the star, but leaving the light from the nearby planet unaffected.

The idea of an optical vortex has been around for many years, but it has never been applied to astronomy before. In lab trials of the optical vortex mask, light from mock stars has been reduced by factors of 100 to 1000, while light from a nearby "planet" was unaffected (see figure).

Attaching their device to a telescope on Mt. Lemon outside Tucson, Arizona, the researchers took pictures of Saturn and its nearby rings to demonstrate the ease of integrating the mask into telescopic imaging system. This is, according to Swartzlander (520-626-3723, grovers@optics.arizona.edu), a more practical technique than merely attempting to cover the star's image, as is done in coronagraphs, devices for observing our sun's corona by masking out the disk of the sun. It could fully come into its own on a project like the Terrestrial Planet Finder, or TPF, a proposed orbiting telescope to be developed over the coming decade and designed to image exoplanets.

A corkscrew shaped lens, eh? It's amazing the topographical capacity in lens engineering. I bet this is all fused silica. When will we have single crystal sciu light sources? I'm in no hurry. I study the magnetic recombinance of solar coronas. No need here for that source type. Let me jump back to times when I could just play games and not worry about lens and abberration and physics. GRRRR! Real life sucks.

The closest extrasolar planet is (according to this [obs-hp.fr]) Gliese 876. It's situatet 15 lightyears from us which works out to 15years*300000km/s*86400s*364.25days=472068000km. The planetary radius is 0.1 times the solar radius (our sun). Which gives a diameter of (according to wikipedia [wikipedia.org]) 1392000km*0.1=139200km. Thus (according to Python) the angle is; atan(139200km/472068000km)~2.9*10^-4 radians, which is ~0.017 degrees. A supprisingly big number in my opinion.

The closest extrasolar planet is (according to this) Gliese 876. It's situatet 15 lightyears from us which works out to 15years*300000km/s*86400s*364.25days=472068000km. The planetary radius is 0.1 times the solar radius (our sun). Which gives a diameter of (according to wikipedia) 1392000km*0.1=139200km. Thus (according to Python) the angle is; atan(139200km/472068000km)~2.9*10^-4 radians, which is ~0.017 degrees. A supprisingly big number in my opinion.

Not to nitpick - but according to Celestia (take it with a grain of salt, of course) Epsilon Eridani (Gliese 144) is closer than Gliese 876 (10.5 ly as opposed to 15.3 ly) and it has at least 2 known planetary satellites. See here: http://www.daviddarling.info/encyclopedia/E/EpsEri .html [daviddarling.info] or google for "Epsilon Eri."

On a side note, Eps Eri C (the smaller planet) seems to orbit about 28 au from its parent star - I would think this would be a perfect candidate for this technology! (I'm too lazy to work out the math right now, however, bonus points to anyone who does.)

The 472,068,000 doesn't include the 300,000km/s. The real number would be 142,009,200,000,000. (also a year is 365.25 days, but the 15 light-year measurement is much less accurate than that I suspect) The page you point to says the planet's average orbit is 0.2 times the earth-sun distance, about 31.5 million km. That gives an angular distance between the star and planet of about 0.0000127 degrees, or 0.045 arcseconds. The hubble can resolve about 0.07 arcseconds, if we can separate the glare from the star bleeding over, then we are close.

This is why you're taught in courses on physics how to estimate things like the weight of the pyramids or the capacitance of clouds (well we were). So you aren't just a slave to your calculator and can actually detect when a number is BS.

Worry not, for New Horizons, set to launch in January, will reach Pluto in Summer 2015 (it's one of the fastest spacecraft we've ever designed, and will get a gravitational slingshot boost from Jupiter.) Among other things, the New Horizons spacecraft will take the first clear pictures of Pluto.

See, free oxygen (O2) doesn't occur anywhere in nature - except where it's created by life.

And you know this because you have witnessed the entirety of nature? Or this has been deduced and isn't actually a fact, but an assumption?

Actually, O2 does appear in places other than our planet (places assumed to be devoid of life), just not in abundance. But even an abundance is only a hint that life exists. There are inorganic processes that can create oxygen. These usually don't create abundant amounts, but we've only witnessed natural processes on a handful of planets and moons. There's always the possibility that some process we haven't witnessed in our own solar system could be creating abundant supplies of oxygen on a planet in another solar system.

Indeed. The real catch is, oxygen tends to get consumed by other common geological and chemical processes. If all life on Earth died today, oxygen would become a trace element in the Earth's atmosphere within a few thousand years (i.e. practically instantaneously on a geological timescale). Whatever process was generating atmospheric O2 would have to be doing it currently and continuously and on a massive scale. Although alternatives are not impossible, so far, there is only one process in nature known to do fit this bill: life. Occam's Razor would suggest if such an atmosphere were discovered, this would be the best assumption to make, rather than proposing new entites (in this case, new, unprecedented plant-wide processes -- of course, astronomy books are full of a history of unprecedented discoveries).

Of course, we'd have more to go on than just O2. Life turns the whole atmosphere topsy-turvy, probability wise. Earth's atmosphere has numerous chemicals in it at levels that are wildly improbable for a world dominated by inorganic processes. If there are other worlds rich in life, the improbable O2 level would just be the tip of the iceberg. A truly living world should be pretty easy to identify with a spectroscope...